From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Marcin Borkowski Newsgroups: gmane.emacs.help Subject: Re: A strange issue with buffer-undo-list Date: Tue, 09 Mar 2021 22:22:30 +0100 Message-ID: <871rcoyqcp.fsf@mbork.pl> References: <87o8gbqs28.fsf@mbork.pl> <8735xm2t3p.fsf@web.de> <87r1l4n2w8.fsf@mbork.pl> <875z2f8xai.fsf@web.de> <87blbtiapu.fsf@mbork.pl> <87r1kp9nfu.fsf@web.de> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="19520"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: mu4e 1.1.0; emacs 28.0.50 Cc: help-gnu-emacs@gnu.org To: Michael Heerdegen Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Mar 09 22:33:43 2021 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lJjz4-0004wO-87 for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 09 Mar 2021 22:33:42 +0100 Original-Received: from localhost ([::1]:54918 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJjz3-0001e6-9Y for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 09 Mar 2021 16:33:41 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:59358) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJjoR-0005Gc-2u for help-gnu-emacs@gnu.org; Tue, 09 Mar 2021 16:22:43 -0500 Original-Received: from mail.mojserwer.eu ([195.110.48.8]:45524) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJjoP-00081m-2U for help-gnu-emacs@gnu.org; Tue, 09 Mar 2021 16:22:42 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by mail.mojserwer.eu (Postfix) with ESMTP id 2E58BE6D7B; Tue, 9 Mar 2021 22:22:39 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at mail.mojserwer.eu Original-Received: from mail.mojserwer.eu ([127.0.0.1]) by localhost (mail.mojserwer.eu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id QbObjPqx5hcj; Tue, 9 Mar 2021 22:22:35 +0100 (CET) Original-Received: from localhost (178235147075.dynamic-3-poz-k-0-1-0.vectranet.pl [178.235.147.75]) by mail.mojserwer.eu (Postfix) with ESMTPSA id 495F5E62F2; Tue, 9 Mar 2021 22:22:35 +0100 (CET) In-reply-to: <87r1kp9nfu.fsf@web.de> Received-SPF: pass client-ip=195.110.48.8; envelope-from=mbork@mbork.pl; helo=mail.mojserwer.eu X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:128378 Archived-At: On 2021-03-09, at 01:32, Michael Heerdegen wrote: > Marcin Borkowski writes: > >> > Seems so. Where they are used - e.g. in the implementation of >> > `transpose-subr', they are important however. You wouldn't want that >> > undoing a transposition would happen in multiple steps uncovering >> > implementation details. >> >> Agreed, although I don't think undo would kick in within one command >> (without explicit undo boundaries). > > Maybe I had not yet completely understood how this works. It seems one > (primitive) undo undoes until it finds a boundary, and boundaries seem > to be implicitly inserted after any command. Then I think the change > group is used in `transpose-subr' to prevent that the transposition or > its undoing is left in a half-done state in case of an error, and it has > more or less no user visible effect if no errors happen. > > Someone should really write a short summary on how the undo system is > implemented, it is not trivial and finding out is also not. Yeah, I'd also like to read that. (I'd like to write it, too, but I'm afraid I might not be competent enough...) Best, -- Marcin Borkowski http://mbork.pl